Many medical analytical techniques, such as blood and urine analysis, rely on centrifugation as part of the testing procedure. Generally, automated devices designed to perform these tests include a built-in centrifuge having a rotatable platter or carousel in which fluid samples are mounted. It is often desirable to separate the carousel rotating function from the analytical functions, in order to conserve resources such as power and/or computer time. Power conservation is especially important if the device is battery operated. To this end, it is attractive to include switching means in the rotatable platter capable of switching on the analytical functions only after the platter has achieved a predetermined rotational rate.
One way of performing this switching function is to rely on the user to activate the analytical function when the platter is rotating at the proper speed. This switching method suffers from the disadvantages of requiring the user to spend valuable time and attention manually actuating the analytical functions of the device. Moreover, manual actuation is not as reliable as an automatic switching means.
One automatic switching means involves the connection of a mechanical switch to the platter. While more reliable than manual switching, mechanical switches are prone to error arising from dirty electrical contacts, broken or worn springs, and broken or worn actuators. Moreover, mechanical switches rely on moving parts with lifetimes adversely affected by the rotational forces generated by the rotating platter.
There is therefore a need for a non-mechanical switch usable with a rotatable platter capable of actuating an electrically connected device, such as an analytical device, upon rotation of the platter to a predetermined speed. The present invention addresses this need.